Uniqueness of the decimal representation of real numbers.


To begin with, the decimal representation of real numbers is not unique. To see this consider


a=0.99999...

I claim that

a=1

To see this note that

10a = 9.99999...
  a = 0.99999...     (subtract)
----------------
 9a = 9          ==> a = 1

In general, there are real numbers that can be expressed either as a number ending in an infinite string of nines or an infinite string of zeros. That's the only way the real representations are not unique! (Proving this is a good exercise ). To obtain a unique decimal representation of a real number we usually impose the convention that it not end in an infinite string of nines.


Fine print, your comments, more links, Peter Alfeld, PA1UM

[16-Aug-1996]